The Veteran Marine — who survived a helicopter crash in Afghanistan in 2012 that resulted in severe injuries and required more than 40 surgeries — had her left leg amputated above the knee at the end of 2015.

“I was intimidated at first,” Ennis admits of the prospect of stripping down for ESPN. But the thought of making a difference for other people going through similar struggles convinced her to say yes.

“I really thought about it and thought about the demographic and the people that would see it and I really realized that it wasn’t about me anymore,” she says. “Any man, woman, or child facing some sort of adversity has a potential to be inspired by these pictures and seeing somebody who only has been missing their leg for a few years go out and do things that she wasn’t doing with two legs.”

And though she says the first moment was the most nerve-wracking, she felt at ease by the end of the process.

“The hardest part was just dropping the robe,” she says. “At a certain point, it’s like, ‘Realistically, this is pretty badass. I don’t know of anybody else in the world that has ever climbed at Joshua Tree with no clothes on.’ “

Ennis is now one of the top Paralympic snowboarders in the world, and is looking forward to (hopefully) competing in PyeongChang next year. She’s also a mountain climber: She took on Kilimanjaro in March, Carstensz in a few weeks, and after that, Everest. Denali is on her schedule for the fall.

Despite these incredible accomplishments, Ennis’s recovery battle continues: Last November, she had to go back into the operating room to have two more inches of her leg removed.

“Curveball after curveball,” she says. “I’ve been blessed with a pretty strong body and I went right back into training as soon as they cleared me to get back up on two feet.”

Her injuries present not only physical hurdles, but mental ones, too. This is where the MVP Foundation — headed up by sports commentator and coach Jay Glazer — comes in. The program supports retired NFL players and combat veterans in their transitions to a life outside of professional sports and the armed forces. The group meets weekly, and after a 30-minute workout session, they all sit down for a “fireside chat” and talk about the importance of living.

“I said, ‘Show of hands, if this group wasn’t here, if we didn’t have this team, how many people in this room probably wouldn’t be alive right now?’ ” Glazer tells PEOPLE of a recent meeting. “And we had about 40 people raise their hands, including Kirstie.”

He says: “It’s just giving them a message of, ‘Different is good. Don’t be afraid to be different. You don’t need to blend in with the rest of society.’ Be proud of every battle scar you have, inside and out, wear that proudly.”

And even in a room of inspiring people who have overcome so much, Glazer says that Ennis stands out.

“She is one of the biggest game-changers of a person you’ll ever come across in your whole life,” Glazer says.

Ennis has inspired countless people, including Prince Harry, who she met at a Walking With the Wounded event in 2015. Following the event, Harry called Ennis his “hero,” and she went on to compete at the 2016 Invictus Games. Ennis won’t be competing in this year’s Invictus Games in Toronto, but hopes to participate in next year’s event, in Sydney, Australia.

“He is a good man with a big heart,” she says of Harry. “He’s definitely his mother’s child.”

Her personal accomplishments mean a lot to Ennis, but nothing has a more of an impact than helping others. She recalls one moment in particular when she was able to inspire a young girl who also wears a prosthetic.

“I like to think I’m pretty tough but kids will bring me to my knees pretty quick,” she says. “There was a little girl at the prosthetics office who had never seen another girl with a prosthetic, let alone a grown-up. She was going into her first day of second grade. And she was just so in awe of me, calling me a princess. I still stay in touch with all of them. Her dad got ahold of me and he’s like, ‘You’ll never know what you just did for my daughter just by being there with her and walking with her.’”